International Islamic University Malaysia

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA END OF SEMESTER EXAMINATION SEMESTER 1, 2013/2014 SESSION KULLIYYAH OF ENGINEERING

Programme : ENGINEERING Level of Study : UG 1

Time : 9:00 am- 12:00 pm Date : 31/12/13

Duration : 3 Hours

Course Code : ECE 1312/ECE 1231 Section(s) : 1 - 8

Course Title : Electronics

This Question Paper Consists of Eight (8) Printed Pages (Including Cover Page) With Five (5) Questions.

INSTRUCTION(S) TO CANDIDATES DO NOT OPEN UNTIL YOU ARE ASKED TO DO SO

 Total mark of this examination is 100.  This examination is worth 45% of the total assessment.  Answer ALL FIVE questions.

Any form of cheating or attempt to cheat is a serious offence which may lead to dismissal.

Q.1 [20 marks]

1 Electronics ECE 1312 / ECE 1231

(a) A full wave rectifier circuit is shown in Fig. 1(a) with the primary voltage, v1 = 220

V(rms) and turns ratio, N1:N2 = 20:1. Assume each diode cut-in voltage, V = 0.65 V. (5+2 marks)

(i) What is the peak value of the output current if R = 1 k ?

(ii) What is the Peak Inverse Voltage (PIV) rating of each diode?

Fig. 1(a)

(b) Fig. 1(b) shows a multiple diode circuit. If each diode cut-in voltage,

V = 0.65 V, determine the diode current, ID1 and the output voltage. (7 marks)

Fig. 1(b)

(c) The clamper circuit is shown in Fig. 1(c) has an input sinusoidal voltage,

V(rms). Sketch the output voltage, against time, t. Assume that diode cut-in voltage, V = 0.65 V. (6 marks)

Fig. 1(c)

Q.2 [20 marks]

(a) The voltage transfer characteristic and its BJT circuit are shown in Fig. 3(a). Assume

that VBE (on) = 0.7 V, VCE(sat) = 0.2 V and β = 120.

(i) Find the value of the resistor, RB by assuming VI = 1.9 V. (5 marks) (ii) Sketch the output load line for the circuit. (5 marks)

Fig. 3(a)

(b) Consider the circuit as shown in Fig. 2(b). Determine IBQ, ICQ and VCEQ for β =100. Sketch the output load line and Q-point by assuming, . (6+4 marks)

Fig. 2(b)

Q.3 [20 marks]

(a) A common-emitter amplifier has output voltage -2.4 V when its input voltage is 250 mV. The collector resistance of the amplifier 1.5kΩ is changed to 2.5kΩ, what is the new gain

of the amplifier? Consider that ro = ∞. (4 marks) (b) Draw the small-signal equivalent circuit and calculate the voltage gain of the circuit is shown in Fig. 3. (b). Assume that the transistor and circuit parameters:

β = 100, VCC = 12 V, VBE(on) = 0.7 V, RC = 6 kΩ, RB = 50 kΩ, VBB = 12 V and

VT = 0.026 V. (8 marks)

Fig. 3(b)

(c) Draw the small-signal equivalent circuit for the common collector amplifier as shown in

Fig. 3(c). Derive the equation for voltage gain of the circuit. (8 marks)

Fig. 3(c)

Q.4 [20 marks]

(a) State two (2) differences between MOSFET and BJT. (4 marks)

(b) Fig. 4(b) shows a NMOS circuit with parameters VTN = 0.6 V and 2 Kn = 0.2 mA/V . Determine the values of VGS, VS and VD. (6 marks)

Fig. 4(b)

(c) Design an n-channel MOSFET circuit is as shown in Fig. 4(c) has the following 2 specifications: VDD = 5 V, VSS = -5 V, Kn= 0.48 mA/V and VTN = 1.5 V. Assume that, IDQ = 0.6 mA, VDSQ= 3.5 V and the MOSFET is operating in the saturation region. (10 marks)

Fig. 4(c)

Q.5 [20 marks]

(a) Determine the small-signal voltage gain, input and output resistances of a common-source amplifier as shown in Fig. 5(a). The circuit parameters are, VDD = 4.5V, RD = 4.7 kΩ, R1 = 120 kΩ, R2 = 47 kΩ and RSi = 4 kΩ. Transistor -1 parameters are Kn = 0.6 mA/V2 and λ = 0.025 V (6 marks)

Fig. 5(a)

(b) Fig. 5 (b) shows an n-channel MOSFET logic gate. (i) Draw the corresponding truth table of the logic gate. (3 marks) (ii) Identify the function of the circuit (AND/OR/NOR/NAND gate). (1 marks)

Fig. 5(b)

(c) An op-amp inverting amplifier circuit is shown in Fig. 5(c). (5 +5 marks)

(i) Derive the close-loop voltage gain of the inverting amplifier, Av = - R2/R1. (ii) Determine the values of R1 and R2, if the gain Av = -10, and the current in the feedback resistor is 10 μA when the output voltage is 5.0 V.

Fig. 5(c)

Useful equations for nMOSFET:

Where,

Useful equations for BJT:

Useful equation for pn-junction: